Need to Avoid Doorway Pages

[cyriac]

Doorway pages are typically large sets of poor-quality pages where each page is optimized for a specific keyword or phrase. In many cases, doorway pages are written to rank for a particular phrase and then funnel users to a single destination.
Whether deployed across many domains or established within one domain, doorway pages tend to frustrate users, and are in violation of Google’s guidelines.

Google's aim is to give users the most valuable and relevant search results. Therefore, Google frowns on practices that are designed to manipulate search engines and deceive users by directing them to sites other than the ones they selected, and that provide content solely for the benefit of search engines. Google may take action on doorway sites and other sites making use of these deceptive practices

[Steve Smith]

Doorway pages are web pages created solely for the purpose of attracting the attention of search engine crawlers in an attempt to boost a site's ranking in the results pages of search engines. Doorway pages are sometimes used by search engine optimization firms.
Doorway pages cannot actually be navigated to through the index page of the website they represent. Rather, doorway pages are intended only to be visible when you search for keywords through a search engine. These doorway pages will have no actual value for the user however, and will only act as click through pages to get to the actual site they are meant to represent.